// @algorithm @lc id=232 lang=cpp 
// @title implement-queue-using-stacks


/**
 * Your MyQueue object will be instantiated and called as such:
 * MyQueue* obj = new MyQueue();
 * obj->push(x);
 * int param_2 = obj->pop();
 * int param_3 = obj->peek();
 * bool param_4 = obj->empty();
 */
class MyQueue {
public:
    list<int> in, out;
    /** Initialize your data structure here. */
    MyQueue() {

    }
    
    /** Push element x to the back of queue. */
    void push(int x) {
        in.push_front(x);
    }
    
    void tryOut(){
        if(!out.empty()) return;
        while(!in.empty()){
            out.push_front(in.front());
            in.pop_front();
        }
    }
    /** Removes the element from in front of queue and returns that element. */
    int pop() {
        tryOut();
        auto data = out.front();
        out.pop_front();
        return data;
    }
    
    /** Get the front element. */
    int peek() {
        tryOut();
        return out.front();
    }
    
    /** Returns whether the queue is empty. */
    bool empty() {
        return  out.empty() && in.empty();
    }
};